Some aircraft use a common wing leading edge flap rotary actuator system (LEFAS) that essentially uses shaft driven geared rotary actuators to rotate the wing leading edge flap. Some known configurations use between two and six assemblies of rotary actuators to drive a control surface, such as a leading edge flap (LEF). Each actuator assembly can include multiple actuator slices or geared segments. Each actuator slice requires a structural hinge fitting that attaches the actuator to the LEF. The hinge fittings are often referred to as “tie bars” because they are typically made from titanium.
FIG. 1 shows an example of a known rotary actuator assembly 100 that includes a machined titanium hinge fitting 102 for each actuator segment (not shown). FIG. 2 shows a perspective view of one of the hinge fittings 102 of FIG. 1. Each hinge fitting 102 is coupled to the inner portion of a control surface 104 at attachment points 106. Hinge fitting 102 includes lugs 108 that are connected to the rotary actuator segments. The control surface 104 moves as the actuator segments rotate. Typically, a hinge fitting 102 is used between each segment of the rotary actuator. Each actuator assembly 100 can include multiple actuator segments, depending on the forces to be encountered on the control surface 104.
Hinge fittings 102 are installed within control surface 104 by inserting shims 110 between each hinge fitting 102, and between the hinge fittings 102 and a spar 112 in the control surface 104. Shear clips 114 are fastened to the sides of each hinge fitting 102 to provide structure for mounting the hinge fittings 102 to the spar 112. Multiple hinge fittings 102 are typically required in order to avoid excessive forces on any one hinge fitting 102 and to allow the hinge fittings 102 to be individually shimmed into place in the presence of surface height variations along the spar 112.
Using individual hinge fittings between rotary actuator segments is very costly to assemble due to the large number of parts involved including multiple actuator segments, a hinge fitting for each actuator segment, four or more shims per hinge fitting, a shear clip between each hinge fitting, and any associated fasteners.